Nozzle for electric dispersion reactor

ABSTRACT

A nozzle for an electric dispersion reactor includes two coaxial cylindrical bodies, the inner one of the two delivering disperse phase fluid into a continuous phase fluid. A potential difference generated by a voltage source creates a dispersing electric field at the end of the inner electrode.

This invention was made with Government support under contract no.DE-AC05-840R21400 awarded by the U.S. Department of Energy to MartinMarietta Energy Systems, Inc., and the Government has certain rights inthis invention.

RELATED APPLICATIONS AND PATENTS

The instant application is a Continuation-In-Part of U.S. patentapplication Ser. No. 035,772, filed Mar. 23, 1993, now U.S. Pat. No.5,464,195, which is a Continuation-In-Part of U.S. patent applicationSer. No. 832,091, filed Feb. 6, 1992, now U.S. Pat. No. 5,207,973, whichis a Divisional of U.S. patent application Ser. No. 441,793, filed Nov.27, 1989, which is now U.S. Pat. No. 5,122,360, issued Jun. 16, 1992,the subject matter of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to the production of metal oxidepowders and, more specifically, to an improved nozzle used in anelectric dispersion reactor in the production of metal oxide powders,for example.

The improved nozzle has two coaxially disposed hollow nonconductingcylindrical bodies, the inner cylindrical body being used to introduce adisperse phase fluid into a continuous phase fluid. The outercylindrical body includes a nonconductive hydrophobic sheath on itsinner wall preventing droplets in the aqueous-phase dispersion fromcollecting on the wall.

BACKGROUND OF THE INVENTION

The development of new ceramic materials is sometimes hindered by theability to reproducibly synthesize high quality starting powders. Theability to control the solid morphology of materials formed from powdersis largely dependent upon controlling particle size and sizedistribution. Control is also dependent upon minimizingparticle-particle interaction. Small particles with a narrow range ofparticle size distribution are generally desired. Alternatively, a gooddistribution of particle sizes may include relatively large particleswhich form the bulk of the material as well as smaller particles usedfor filling the interstitial spaces between the larger particles duringmanufacture. A number of methods have been developed to formmonodispersed powders (i.e., particles with a narrow range of particlesize distribution and low tendency toward agglomeration) by chemicalmethods such as the controlled homogeneous precipitation of metal oxidesfrom metal alkoxide by hydrolysis in organic liquid systems. Thesemethods prove to be quite good at producing high purity metal oxidepowders. In many cases, however, the conditions which are favorable formetal alkoxide hydrolysis, and the subsequent metal oxide precipitation,are not amenable to minimizing particle-particle interactions.Consequently, the powders form agglomerates and become polydispersed.Other attempts to produce monodispersed metal oxide powders using thetechnique of metal alkoxide hydrolysis have involved the use ofmechanical stirrers to disperse the aqueous phase in the organic liquidsystem. These techniques are energy intensive and generally do notproduce metal oxide powders with the desired size distribution.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide a methodfor preparing metal oxide powder within a desired range of sizedistribution and with a minimum of particle-particle interactions.

It is a further object of the present invention to provide a method andapparatus for preparing monodispersed metal oxide powders which possessoptimum morphology and surface properties for use as ceramic precursors.The apparatus utilized in accomplishing the instant invention includes areaction nozzle that facilitates the preparation of metal oxide powder.

Another object of the present invention is to provide a reaction nozzlepermitting high capacity dispersion operations at high dispersionconcentrations.

In general, this invention relates to processes for formingmonodispersed powders by forcing particle growth in localized reactionzones. These reaction zones are created by the dispersion ofmicro-droplets of a disperse phase fluid within a continuous phasefluid. Small particles (0.1-5 micrometers) are produced because thediffusion and reaction of the dispersed micro-droplet occurs veryrapidly. Formation and dispersion of submicron-sized micro-dropletswithin a relatively nonconducting continuous phase is accomplishedthrough the use of high-intensity-pulsed electric fields, i.e., pulsedfields with strengths greater than 1 kilovolt per centimeter. Theseelectric fields are produced within the outer cylindrical body of thereaction nozzle where the disperse phase and continuous phase fluidreact.

Throughout the body of this disclosure the term "disperse phase fluid"indicates a solution, or material, which is atomized into micro-dropletswhen the appropriate electric field is applied. The term "continuousphase fluid" refers to the fluid into which the disperse phase fluid isdispersed. In a preferred embodiment the continuous phase fluid isdielectric and thus is unaffected by the electrical field, and reactswith the atomized disperse phase fluid, which is preferablyelectrolytic, to form metal hydroxide or metal oxalate particles.

The present invention provides a method for preparing metal oxidepowders. Briefly, the method comprises preparing a first solution whichis a non-conductive continuous phase fluid. This first solution ispreferably a substantially organic solution. A second solution,comprising a conductive disperse phase fluid that is substantiallyimmiscible in the first solution, is prepared and delivered to thesecond solution. This second solution is preferably an aqueous solution.The second solution is then introduced within the first solution. Thesecond solution is atomized by a pulsed electrical field formingmicro-drops of the second solution. Reagents in the first solutiondiffuse into and react with the micro-drops of the second solution toform metal hydroxide or metal oxalate particles. The particles are thenrecovered and dried to produce the metal oxide powder. It should benoted that the continuous phase fluid could be conductive and thedisperse phase fluid could be non-conductive, although the preferredembodiment utilizes the alternate arrangement.

In one embodiment of the present invention the first solution comprisesa metal alkoxide and the second solution comprises an aqueous solution.The aqueous solution is chosen from the group consisting of neutral,acidic and basic aqueous solutions. In another embodiment of theinvention, the first solution is a liquid metal alkoxide. Otherembodiments of the invention include those where the metal alkoxidecomprises a metal chosen from the group consisting of main group metals,transition metals, alkali and alkaline earth metals and lanthanides andactinides. The alkoxide is chosen from the group consisting ofderivatives of straight chain and branched chain alcohols.

Another embodiment of the present invention provides that the firstsolution comprises an alcohol and the second solution comprises anaqueous solution with a water soluble metal salt. In one embodiment ofthe invention the first solution comprises an alcohol and ammonia. Inadditional embodiments of the invention the water soluble metal saltcomprises a metal chosen from the group consisting of main group metals,transition metals, alkali and alkaline earth metals and lanthanides andactinides. In addition, precipitation agents are chosen from the groupconsisting of ammonium hydroxide and oxalic acid. The alcohol in anotherembodiment of the invention comprises straight chain and branched chainalcohols having more than two carbons in the chain.

In a first embodiment of the invention a pulsed electrical field isgenerated by producing a direct current (D.C.) voltage offset withsuperimposed voltage spikes. The voltage level of the spikes is betweenabout two kilovolts per centimeter and about 100 kilovolts percentimeter with the constant D.C. offset being about 50% of this value.The voltage spikes of the electric field are produced at a frequency ofbetween about 100 Hz and about 3,000 Hz. The first embodiment utilizes areaction vessel in combination with a pair of electrodes to achieve thedesired results. In use, a drop of a conductive disperse aqueous phaseis introduced into the reaction vessel that is filled with thenon-conductive continuous organic phase. At this point, the solutionsreaction in the manner previously described.

A second embodiment is also provided for preparing metal oxide powders.The apparatus comprises a reaction nozzle for containing a flow of afirst solution that is preferably a non-conductive organic solution anda second solution preferably comprising a conductive aqueous solutionthat is substantially immiscible in the first solution. A hollow innercylindrical body is provided for delivering the second solution into thefirst solution. Also, a hollow outer cylindrical body is provided forcontaining a flow of the first solution. A voltage source interacts withan electrode located outside of the outer cylindrical body to apply apulsed electrical field to the second solution. The pulsed electricalfield fractures the second solution to form micro-drops. The firstsolution then reacts with the micro-drops of the second solution to formmetal hydroxide or metal oxalate particles. The particles are finallyheat treated to produce a metal oxide powder.

The preferred reaction nozzle includes a hollow inner cylindrical body.The inner cylindrical body is nonconductive and preferably constructedfrom glass. The inner cylindrical body is coaxially disposed within ahollow outer cylindrical body, which is also nonconductive andconstructed from glass. The outer cylindrical body includes anonconductive hydrophobic sheath along its inner wall. The coaxialbodies create an annular space through which the organic solution flowsin a high flow velocity fashion. In use, the outer cylindrical body andthe inner cylindrical body are dielectric and remain uncharged. Anelectrical field is generated by a charged electrode positioned outsideof the outer cylindrical body. This electrode creates the electricalfield necessary to generate the dispersion discussed above.

The use of nonconducting inner and outer cylindrical bodies, incombination with the hydrophobic sheath, minimizes the build-up of theconducting dispersed phase material in the electrode region.Additionally, the positioning of the electrode prevents the occurrenceof short circuits. The coaxial arrangement of the inner cylindrical bodyand the outer cylindrical body eliminates arcing and solid build up thatoccurs in reactors having exposed nozzles and electrodes in low velocityregions. Additionally, the configuration creates a very high electricfield strength in the electrode region which enhances dispersion of thedisperse phase solution.

When using the instant reaction nozzle, the velocity of the continuousorganic phase is very high. This enhances the removal of disperse phasefluid from the electrode region. Further, the disperse aqueous phase,that is subjected to the electrical fields, has an internal pressurehigher than the pressure of the continuous organic phase. Thus, thedispersion is more easily swept pass the outer cylindrical body region,in addition to the enhanced dispersion and the effects of the flow ofthe continuous organic phase. This minimizes the build-up of dispersedconducting materials in the reaction nozzle region and allows theformation of a more concentrated dispersion in areas of the reactoroutside the reaction nozzle.

As a result, the instant reaction nozzle encourages the formation ofceramic precursor particles by providing a continuous phase flowvelocity that is similar to, or greater than, the disperse phase flowvelocity. Particle formation is also encouraged by the electric fieldinduced stresses that propel the dispersion away from the innercylindrical body and out of the reaction nozzle region.

During a typical operation, a flow of the disperse aqueous phasesolution is introduced into a continuous phase of a substantiallyorganic solution. The disperse aqueous phase is introduced through theinner cylindrical body which is uncharged. An electric field is appliedto the first solution by the energized electrode position outside theouter wall of the outer cylindrical body. A voltage is applied to theelectrode such that the generated electric field is a pulsed D.C.electric field having a voltage between about 15 kilovolts and about 30kilovolts.

When the continuous phase contains a liquid metal alkoxide and theaqueous phase contains water which is either neutral, acidic or basic,then it is believed that the following reactions take place in themicro-droplets. It is believed that initially there is a hydrolysisreaction as is shown in reaction (1). The metal is designated by "M" andhas a valence n.

    M(OR).sub.n +nH.sub.2 O--M(OH).sub.n (ppt.)+nROH           (1)

The metal alkoxide is converted in the presence of water into a metalhydroxide with the alkoxide coming off as alcohol, ROH. The metalhydroxide particles then precipitate out of the solution. The metalhydroxide, M (OH)_(n), is then collected and dehydrated in a dryeraccording to reaction (2) forming the metal oxide.

    M(OH).sub.n --MO.sub.n/2 +(n/2) (H.sub.2 O)                (2)

The metal oxide powders produced by this method are highly porous shellsand flakes. The powder is a fine, homogeneous, free-flowing metal oxide.The powder may be used for packaging material (i.e., for electroniccomponents) or, because of their high surface area, as chromatographicand catalytic support materials.

Rather than having the metal as a metal alkoxide in the continuousphase, the metal may be a part of a water soluble metal salt which isdissolved in the aqueous phase solution. In this case, the continuousphase comprises an alcohol or an alcohol with oxalic acid. In operation,the formation of the micro-drops is similar to that described above. Thereactions forming the metal hydroxide or metal oxalate particles andmetal oxide powders, reactions (3)-(5) are believed to be similar toreactions (1) and (2) above.

The formation of a metal oxide powder from an alcoholic continuous phaseis believed to follow the steps shown in reactions (3) and (4).

    M.sup.n+ +nOH.sup.- →M(OH).sub.n (ppt.)             (3)

    M(OH).sub.n →MO.sub.n/2 +(n/2) (H.sub.2 O)          (4)

The formation of a metal oxide powder from an alcoholic continuous phasecontaining oxalic acid is shown in reactions (5) and (6).

    mM.sup.n+ +(mn/2)H.sub.2 C.sub.2 O.sub.4 →M.sub.m (--C.sub.2 O.sub.4).sub.(mn/2) (ppt.)+mnH.sup.30                     ( 5)

    M.sub.m (C.sub.2 O.sub.4).sub.(mn/2) +(mn/2)O.sub.2 →mMO.sub.n/2 +mnCO.sub.2                                               ( 6)

The metal oxide powders formed using the water soluble metal saltscomprise dense, spherical particles. These dense particles are alsosuitable for forming high density ceramic articles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a first embodiment of an apparatus forproducing powders according to the present invention, based on batchprocessing;

FIG. 2 is a schematic diagram of a second embodiment of an apparatus forproducing powders according to the present invention, employing acontinuous flow reaction nozzle;

FIG. 3 is a side elevational view of a nozzle and container capable ofuse in the apparatus illustrated in FIG. 2; and

FIG. 4 is an enlarged, vertical cross-sectional view of the nozzle ofFIG. 3.

FIG. 5 is an enlarged, horizontal cross-section view of the nozzle ofFIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings in which like reference charactersdesignate like or corresponding parts throughout the several views,there is shown in FIG. 1 an embodiment of an apparatus 10 for producingmetal oxide powder in accordance with the present invention. Thedepicted apparatus 10 generally comprises a reaction vessel 12 forcontaining a continuous phase fluid 14, which is preferably organic anddielectric (or electrically non-conductive). The reaction vessel 12 maybe of any number of shapes but in one embodiment the reaction vessel 12is an open cylinder with a closed bottom 16 joined to the cylindricalside wall 18. The continuous organic phase fluid 14 is loaded into thereaction vessel 12. A reaction vessel cover 20 is placed onto the top ofthe reaction vessel 12 providing a gas tight seal at the side wall 18.The reaction vessel cover 20 is fitted with ports 22 for purging thehead space 24 of the reaction vessel.

The reaction vessel 12 is also fitted with electrodes 26 which areplaced in intimate contact with the continuous organic phase 14 and thencontinue through the head space 24 and the reaction vessel cover 20 to apulsed electric field source 28. The pulsed electric field source 28provides a pulsed electric signal which creates an offset D.C. voltagewith superimposed spikes.

There is also provided a nozzle 30 for the delivery of drops of aqueoussolution 32. The nozzle 30 is constructed of conductive material such asmetal and is connected to an electrical ground 34. The presence of apulsed field on the electrodes 26 and ground 34 at the nozzle 30generates a pulsed electric field between the electrodes 26 and thenozzle 30. Upon exit from the nozzle 30, the drop of aqueous solution 32is fractured into aqueous micro-drops 36. The micro-drops 36 react withthe continuous organic phase fluid 14 and form solid metal hydroxideparticles 38 which drop to the bottom of the reaction vessel 12. Uponthe completion of the addition of the drops of aqueous solution 32 tothe continuous organic phase fluid 14 in the presence of the pulsedelectric field the resulting metal hydroxide particles 38 are recovered,filtered or centrifuged and dried to produce the metal oxide powder.

The metal is contained in the continuous organic phase fluid 14 or inthe drops of aqueous solution 32 as desired. The metal is present as ametal alkoxide when it is present in the continuous organic phase fluid14 and it is present as a water soluble metal salt when it is in thedrops of aqueous solution 32.

In operation, the apparatus 10 is prepared by filling the reactionvessels 12 with the continuous organic phase fluid 14. In the followingdescription it will be assumed that the continuous organic phase fluidcomprises a metal alkoxide and that the drops of aqueous solutioncomprise an aqueous solution that is either neutral, basic or acidic. Asimilar operation is used where the continuous organic phase fluid 14comprises an alcohol and the drops of aqueous solution 32 comprise awater soluble metal salt in water.

The reaction vessel cover 20 is placed on the reaction vessel 12 and thehead space 24 is purged with the ports 22. The purging usually involvesthe replacement of air in the head space 24 with a nonflammable gas suchas nitrogen. A pulsed electric field is developed between the electrodes26 and the nozzle 30. This electric field contains two components: aD.C. voltage offset of between about 2 kilovolts per centimeter andabout 100 kilovolts per centimeter. The spikes are pulsed at a frequencybetween about 100 Hz and about 3,000 Hz.

Drops of the aqueous solution 32 are introduced into the continuousorganic phase fluid 14 and are immediately atomized by the pulsedelectric field creating aqueous micro-drops 36. These micro-drops 36have sizes in the micrometer range and are dispersed throughout thecontinuous organic phase fluid 14. The continued application of thepulsed electric field maintains the micro-drops in a dispersed statethrough the continuous organic phase fluid 14. The metal alkoxide of thecontinuous organic phase fluid 14 reacts with the aqueous solution ofthe micro-drops 36 forming metal hydroxide particles 38 whichprecipitate out of the continuous organic phase fluid 14. The reactionof the metal alkoxide with the aqueous micro-drops 36 is sufficientlyrapid that an entire micro-drop 36 is converted to a metal hydroxideparticle 38. The metal hydroxide particle 38 that is formed is smallerthan the aqueous micro-drops 36 from which it formed.

Aqueous micro-drops 36 are added to the continuous organic phase fluid14 for a period of about 10 minutes. At the end of that time, the pulsedelectric field is removed and the metal hydroxide particles 38 areallowed to settle to the bottom 16 of the reaction vessel 12. Thereaction vessel cover 20 is removed and the continuous organic phasefluid 14 containing the metal hydroxide particles 38 is filtered torecover the metal hydroxide particles 38. The particles 38 are washedand heat treated for the metal oxide.

The dried product is a fine, homogeneous, free-flowing metal oxidepowder. The powder particles have sizes that range from about 0.1micrometers to about 2 micrometers and are porous and flaky when dried.

A similar procedure is followed when the continuous organic phase fluid14 comprises an alcohol and the drops of aqueous solution 32 comprise awater soluble metal salt dissolved in an aqueous solution. The metaloxide powders which result from that combination of solutions aregenerally dense and spherical.

Another embodiment of the present invention is shown in FIG. 2. Thisembodiment includes an apparatus 40 for the continuous production ofmetal oxide powder. The apparatus comprises a reaction vessel 42 whichcontains a continuous organic phase fluid 44. The organic phase fluid 44is moved through the reaction vessel 42 in the direction of arrows 46.The organic phase fluid 44 is supplied from an organic phase storage 48which is external to the reaction vessel 42. The organic phase fluid 44is supplied to the reaction vessel 42 from the storage 48 along conduit50 to an organic phase fluid supply pump 52, such as a Masterflex pump.The supply pump 52 is connected to the reaction vessel 42 by conduit 54which contains a supply shut-off valve 56. The opposite end of conduit54 is connected to a T-connector 58 which output 60 is connected toreaction vessel organic phase fluid connection 64.

An aqueous phase fluid storage 66 contains the aqueous phase fluid 68which is supplied to the reaction vessel 42. A conduit 70 connects theaqueous phase fluid storage 66 with an aqueous phase fluid supply pump72. The output of the aqueous phase fluid supply pump 72 is connected toa conduit 74 which contains an aqueous phase supply shut-off valve 76.The opposite end of conduit 74 is attached to one end 78 of an aqueousphase nozzle 80. The aqueous phase fluid 68 travels down the aqueousphase nozzle 80 to the other end 82 which is submerged in the continuousorganic phase fluid 44 of the reaction vessel 42. A drop 84 of theaqueous phase 68 is released from the end 82 of the aqueous phase nozzle80 into the continuous organic phase 44. In a process to be described inmore detail hereinafter, the drop 84 is atomized into micro-drops 86which react with the continuous organic phase 14 to form metal hydroxideparticles 88.

The metal hydroxide or metal oxalate particles 88 and continuous organicphase fluid 44 are removed from the reaction vessel 42 at the exit port90. The exit port 90 is connected to the conduit 92, the distal end ofwhich is connected to a product pump 94. The continuous organic phasefluid 44 containing the metal oxide particles 88 is pumped along aconduit 96, through a valve 98, to an electrical bed filtration unit100. In the electrical bed filtration unit 100 a filter element 102,such as glass beads, is electrically connected to a filter power supply104, such as a Hyptronics Model 825C High Voltage D.C. Power Supply. Thefilter power supply 104 applies a voltage across the filter unit 102thereby trapping the metal hydroxide or metal oxalate particles 88 onthe particulate side 106 of the electrical bed filter unit 100. Thisallows the continuous organic phase fluid 44 to pass through the filterunit 102 to the filtrate side 108 of the filtration unit 100. Thefiltrate is then returned to the reaction vessel 42 along the conduit110 to the T-connector 112. One output side of the T-connector 112 isconnected to conduit 114, which is also joined to T-connector 58,thereby returning the continuous organic phase fluid 44 to the reactionvessel 42. Alternatively, a valve 116 provided in conduit 118 may beopened to allow passage of the continuous organic phase fluid 44 to afiltrate storage 120.

The aqueous phase nozzle 80 of the reaction vessel 42 is connected by aconnector 122 to an electrical ground 124. There are electrodes 126which are submerged in the continuous organic phase fluid 44 of thereaction vessel 42 in the vicinity of the end 82 of the aqueous phasenozzle 80. The electrodes 126 are connected to an electrical field powersupply 128, such as a Velonix Model 660 High Voltage Pulse Generator,through the wire 130. The electrical field power supply 128 supplies anelectrical signal to the electrodes 126 which is comprised of an offsetD.C. voltage which has voltage spikes riding atop the D.C. offset. Thevoltage applied to the electrodes 126 from the electrode power supply128 may be positive or negative without affecting the efficiency of thesystem. The presence of the pulsed electric field generated between theelectrodes 126 and the grounded aqueous phase nozzle 80 operates toatomize the drop 84 into micro-droplets 86. Those micro-droplets 86 thenreact with the continuous organic phase fluid 44 producing the metalhydroxide or metal oxalate particles 88.

In operation, the reaction vessel 42 is loaded with a continuous organicphase fluid 44 from the organic phase storage unit 48. When the reactionvessel 42 is at its capacity, the continuous organic phase fluid 44 isrecirculated through the electrical bed filtration unit via the conduit92, the product pump 94, the conduit 96, the valve 98, the electricalbed filtration unit 100, the conduit 110, the T-connection 112, theconduit 114, the T-connection 58 and the conduit 62. This recirculationis continued until the continuous organic phase 44 is exhausted. At thattime, the valve 116 in the conduit 118 is opened and the exhaustedcontinuous organic phase fluid 44 is placed into the filtrate storageunit 120.

The aqueous phase fluid 68 is loaded into the reaction vessel 42 fromthe aqueous phase storage 66. The aqueous phase fluid 68 is applieddropwise to the continuous aqueous phase fluid 44. As each drop 84emerges from the end 82 of the aqueous phase nozzle 80 it is atomizedinto micro-drops 86 by the pulsed electrical field generated between theelectrodes 126 and the ground 124 attached to the aqueous phase nozzle80. The reagents in the continuous organic phase fluid 44 react withaqueous solution 68 in the micro-drops 86 to form the metal hydroxide ormetal oxalate particles 88. The continuous organic phase 44 and themetal hydroxide particles 88 are then swept toward the exit port 90 ofthe reaction vessel 44 and into the recirculation loop. In theelectrical bed filtration unit 100, the metal hydroxide particles 88 aretrapped by the filter element 102 on the particulate side 106 of thefiltration unit 100. The continuous organic phase fluid 44 is thenreturned to the reaction vessel 42 as previously described.

The metal hydroxide or metal oxalate particles 88 may be removed fromthe electrical bed filtration unit 100 and recovered by washing anddrying to produce a metal oxide powder. The powders produced using thisapparatus are fine, homogeneous and free-flowing.

In order to provide a better understanding of the present invention thefollowing examples are given by way of illustration and not by way oflimitation.

EXAMPLE I

A reaction vessel was filled with a continuous organic phase comprisinga metal alkoxide of a type listed in Table I. A pulsed electric fieldwith a field strength of 5 kV/cm offset D.C. with 10 kV/cm spikes wasapplied to the continuous phase. An aqueous disperse phase of the typelisted in Table I was injected into the continuous phase from a grounded0.125 cm syringe tip in the vicinity of the pulsed electric field. Thedrops emerging from the syringe tip were readily atomized intomicro-drops which were dispersed in the continuous phase. The continuousphase reacted immediately with the micro-drops to form the metalhydroxide particles. The metal hydroxide was formed in yields of greaterthan 99.5%. Upon completion of the addition of the aqueous phase, thereaction solution was filtered and the metal hydroxide was recovered.The metal hydroxide was dried at 100° C. for 24 hours. Table I lists adescription of the final hydrous metal oxide powder. In all cases, thepowders were fine, homogeneous, monodisperse, free-flowing powders.

                  TABLE I    ______________________________________          Continuous    Sample          Phase      Disperse Phase                                 Product    ______________________________________    A     TEOS.sup.1 0.7M NH.sub.3 in                                 Porous silica shells                     water    B     2-EH.sup.2 with                     water       Well mixed submicron          TIE.sup.3 /ASB.sup.4   powder containing          (1/3)                  hydrous alumina and                                 titania in a molar                                 ratio of 3:1    C     2-EH with  water       Well mixed submicron          TIE/ABS.sup.5          powder containing                                 hydrous alumina and                                 titania in a molar                                 ratio of 3:1    D     2-EH with  water       Well mixed submicron          ASB/ZB.sup.6           powder containing                                 hydrous alumina and                                 zirconia in a molar                                 ratio of 2.6:1    E     2-EH with  water       Well mixed submicron          ABS/ZB                 powder containing          (2.6/1)                hydrous alumina and                                 zirconia in a molar                                 ratio of 2.6:1    ______________________________________     .sup.1 Tetraethylorthosilicate     .sup.2 2ethyl 1hexanol     .sup.3 titanium ethoxide     .sup.4 aluminum secbutoxide     .sup.5 aluminum butoxide stearate     .sup.6 zirconium butoxide

EXAMPLE II

A reaction vessel was filled with a continuous organic phase comprisingan alcohol mixture of the type listed in Table II. A pulsed electricfield with a field strength of 5 kV/cm offset D.C. and 5 kV/cm spikeswas applied to the continuous phase. An aqueous disperse phase with ametal salt mixture of the type listed in Table II was injected into thecontinuous phase from a grounded 0.125 cm syringe tip in the vicinity ofthe pulsed electric field. The drops emerging from the syringe tip werereadily fractured into micro-drops which were dispersed in thecontinuous phase. The continuous phase reacted immediately with themicro-drops to form the metal hydroxide or metal oxalate particles. Themetal hydroxide or metal oxalate was formed in yields of greater than99.5%. Upon completion of the addition of the aqueous phase, thereaction solution was filtered and the metal hydroxide was recovered.The metal hydroxide was dried at about 150° C. for 24 hours. Table IIlists a description of the final metal oxide powder. In all cases, thepowders were fine, homogeneous, monodisperse, free-flowing powders.

                  TABLE II    ______________________________________          Continuous    Sample          Phase       Disperse Phase                                  Product    ______________________________________    F     2-EH/EtOH.sup.7                      aqueous metal                                  0.1 to 2 micron          (95:5 vol %)                      nitrate solution                                  spherical particles          with 0.2M NH.sub.3                      Y/Ba/Cu     containing mixed                      (1:2:3)     oxides of Y, Ba and                                  Cu with a molar ratio                                  of about (1:2:3)    G     2-EH/EtOH   aqueous metal                                  0.1 to 2 micron          (95.5 vol %)                      nitrate solution                                  spherical particles          with 0.2M NH.sub.3                      of Cu       containing oxides of                                  Cu    H     2-EH/EtOH   aqueous metal                                  0.1 to 2 micron          (95.5 vol %)                      nitrate solution                                  spherical particles          with 0.2M NH.sub.3                      of Cu       containing oxides of                                  Cu    I     2-EH/       aqueous metal                                  Submicron sized          CYHEX.sup.8 /                      nitrate solution                                  spherical particles          EtOH with   Y/Ba/Cu     containing mixed          0.2M NH.sub.3                      (1:2:3)     oxides of Y, Ba and                                  Cu with a molar ratio                                  of about (1:2:3)    J     2-EH with 2%                      aqueous metal                                  Submicron sized          by weight of                      nitrate solution                                  spherical particles          oxalic acid of Y        containing mixed                                  oxide of Y    K     2-EH with 2%                      aqueous metal                                  Submicron sized          by weight of                      nitrate solution                                  spherical particles          oxalic acid of Ba       containing mixed                                  oxide of Ba    L     2-EH with 2%                      aqueous metal                                  Submicron sized          by weight of                      chloride    spherical particles          oxalic acid solution of Cu                                  containing mixed                                  oxide of Cu    ______________________________________     .sup.7 ethanol     .sup.8 cyclohexane

Referring now to FIGS. 3, 4 and 5, an alternative nozzle 132 for anelectric dispersion reactor can be used in the apparatus of FIG. 2 tosupplant the reaction vessel 42. The nozzle 132 includes annonconductive outer cylindrical body 134. The outer cylindrical body 134is preferably made of glass, although other nonconductive materials canbe used while remaining within the spirit of the present invention.

The outer cylindrical body 134 is annular and includes a nonconductivehydrophobic sheath 136 covering its inner wall 138. The hydrophobicsheath 136 is preferably polyolefin, although other materials can beused. The hydrophobic sheath 136 hinders the droplets in the aqueousphase dispersion from collecting on the inner wall 138 of the outercylindrical body 134.

Additionally, the outer cylindrical body 134 has an open upper end 140for receiving the continuous phase fluid and an open bottom 142 whichfunctions as a fluid outlet for the continuous phase material. A teflonT-shaped inlet 144 is secured to the upper end 140 of the outercylindrical body 134. The T-shaped inlet 144 can be coupled to thecontinuous phase fluid storage 46 of FIG. 2 through conduit 62.

An inner cylindrical body 146 has a central opening 148 and delivers adisperse phase fluid at a predetermined flow rate into the continuousphase fluid. Preferably, the inner cylindrical body 146 is made of anonconductive material, such as glass, and includes an inlet 150 whichcan be connected to the storage 66 for disperse phase fluid throughconduit 74, and an outlet 148.

The inner cylindrical body 146 is mounted coaxially with the outercylindrical body 134 by a flange 152 secure at the upper end of theT-shaped inlet 144. The coaxial arrangement of the outer cylindricalbody 134 and the inner cylindrical body 146 creates an annular space 154through which the continuous phase fluid passes.

An electrode 156 is positioned outside of the outer cylindrical body 134at a position just below the outlet 158 of the inner cylindrical body146. The location of the electrode 156 outside the outer cylindricalbody 134 prevents short circuits from occurring between the inner andouter cylindrical bodies 146, 134. The electrode 156 is a metal ring,and is 0.1 in. wide by 0.075 in. height in its preferred embodiment.With the disperse phase fluid being grounded, a transient electric fieldcomprised of alternating positive and negative pulses is used to inducecharge on the inside of the nonconducting hydrophobic sheath 136, whichin turn forms the electric field causing the droplet break-up at theoutlet 158 of the glass inner cylindrical member 146. A voltage source(VS) 160 shown in FIG. 4 generates the electric field at a locationwithin the outer cylindrical body 134 where the disperse phase entersthe continuous phase. The voltage source 128 illustrated in FIG. 2 canbe modified to accommodate the nozzle of FIGS. 3, 4 and 5. The preferredsource is a pulsed D.C. source as described previously with respect toFIG. 2.

A non-electrically conductive mounting plate 162 is used to mount thenozzle 132 to the container 162, although any suitable mounting meanscan be employed instead. Moreover, the nozzle 132 can be mounted inother processing systems which require the electric dispersion of onefluid into another.

The lower end of the container 162 is provided with an outlet 164 whichcan be coupled to the conduit 92 of the apparatus described in FIG. 2 sothat the continuous phase fluid, containing dispersed particles, can becommunicated to a separation stage.

The nozzle of FIGS. 3, 4 and 5 was tested using 2-ethyl 1-hexanol as thecontinuous phase and an aqueous phase comprised of very dilute tosaturated solutions of yttrium nitrate, zirconyl nitrate, aluminumnitrate, aluminum sulfate, barium chloride, cupric chloride and variousother salts. The continuous phase was supplied at a rate between about 0and 400 cc/min., while the disperse phase flowed at approximately 10% ofthe continuous phase flow rate (i.e., approximately between about 0 and40 cc/min.). The electrical parameters were peak voltages of 40 Kv andpulse frequencies of up to 5 kHz. The present embodiment produced good,consistent dispersions with no arcing at dispersed phase concentrationsup to 4%.

In most cases, the continuous phase material flows continuously throughthe inner cylindrical body at a predetermined flow rate towards thecollection area 166 defined by container 164, and the disperse phasefluid flows through the annular space 154 in the outer cylindrical body134. The continuous phase material is dielectric and the disperse phasefluid is electrolytic or electrically conductive, or otherwise have asignificant difference in electrical conductivity. The flow ofcontinuous phase fluid past the outlet 158 of the inner cylindrical body146 ensures the removal of the dispersion from the electrode region, andallows a more efficient removal and separation.

According to the present invention, the organic or continuous phasefluid has a flow velocity that is similar to the aqueous or dispersephase fluid velocity, or greater. The voltage source 150 generates apulsed D.C. electric field that generates electric field inducedstresses so great that the dispersion is propelled away from the outlet158 of the inner cylindrical body 146.

The diameters of the reaction nozzle parts are proportionally related,in the illustrated embodiment. In one embodiment of the presentinvention, the outer cylindrical body 134 has an outer diameter of 0.375in. and an inner diameter of 0.280 in.; the hydrophobic sheath 136 has athickness of 0.030 in.; and the inner cylindrical body 146 has an outerdiameter of 0.125 in. and an inner diameter of 0.015 in.

As discussed above, flow rates for an aqueous disperse phase fluid andan organic continuous phase fluid range from 0 to 40 cc/min and 0 to 400cc/min, respectively. At these flow rates, drops are dispersed into verysmall droplets with relatively low voltage settings. At low flow ratesfor the disperse phase fluid the dispersion is readily swept away fromthe electrode region with very little to no organic continuous phasefluid flow. With increasing flow rates of disperse phase fluid, the flowrate of the continuous phase fluid must also be increased to ensureremoval of the dispersion from the electrode region. The above flowrates were accomplished using a nozzle having the dimension discussedabove.

It will be noted from the above that the present application providesfor a method and apparatus for the production of metal oxide or otherpowders with particle sizes in the sub-micron range. It will also benoted that these particles are monodispersed and quite suitable for useas ceramic precursors, among other things. In addition, it may be seenthat metal oxide powders which have porous and flaky particles may beproduced as well as metal oxide powders which have spherical and denseparticles.

Various of the features of the invention which are believed to be neware set forth in the appended claims.

What is claimed is:
 1. A nozzle for an electric dispersion reactor,comprising:first means for delivering a continuous phase fluid to acollection area, the first means being electrically nonconductive; ahydrophobic sheath covering an inner wall of the first means; secondmeans, in fluid communication with the first means, for delivering adisperse phase fluid into the continuous phase fluid, the second meansbeing electrically nonconductive; and voltage means for generating anelectric field at a location within the first means where the dispersephase enters the continuous phase, the electric field having anintensity sufficient to disperse the disperse phase fluid into thecontinuous phase fluid.
 2. A nozzle for an electric dispersion reactor,comprising:first means for delivering a continuous phase fluid to acollection area, the first means being electrically nonconductive;second means, in fluid communication with the first means, fordelivering a disperse phase fluid into the continuous phase fluid, thesecond means being electrically nonconductive; and voltage means forgenerating an electric field at a location within the first means wherethe disperse phase enters the continuous phase, the electric fieldhaving an intensity sufficient to disperse the disperse phase fluid intothe continuous phase fluid; wherein the first means includes a hollowouter cylindrical body having a fluid inlet and an open end serving as afluid outlet.
 3. A nozzle for an electric dispersion reactor accordingto claim 2, wherein the second means includes a hollow inner cylindricalbody having a fluid inlet and an open end serving as a fluid outlet, thehollow inner and outer cylindrical bodies being substantially coaxial.4. A nozzle for an electric dispersion reactor according to claim 2,wherein the hollow outer cylindrical body includes a hydrophobic sheathcovering an inner wall of the outer cylindrical body.
 5. A nozzle for anelectric dispersion reactor according to claim 4, wherein thehydrophobic sheath is electrically nonconductive.
 6. A nozzle for anelectric dispersion reactor according to claim 5, wherein thehydrophobic sheath is made from polyolefin.
 7. A nozzle for an electricdispersion reactor according to claim 1, wherein the disperse phasefluid is electrolytic and the continuous phase fluid is dielectric.
 8. Anozzle for an electric dispersion reactor according to claim 1, whereinthe voltage means includes a current source in electrical contact withan external electrode positioned outside of the first means.
 9. A nozzlefor an electric dispersion reactor according to claim 1, wherein thehydrophobic sheath is electrically nonconductive.
 10. A nozzle for anelectric dispersion reactor according to claim 1, wherein thehydrophobic sheath is made from polyolefin.
 11. A nozzle for an electricdispersion reactor according to claim 1, wherein the first means and thesecond means are made from glass.
 12. A nozzle for an electricdispersion reactor according to claim 1, wherein the voltage meansincludes an electrode positioned externally of the first means.
 13. Anozzle for an electric dispersion reaction according to claim 11,wherein the electrode encircles the first means.
 14. A nozzle for anelectric dispersion reactor comprising:an electrically nonconductiveouter body having an axial fluid passageway and an open end, wherein theouter body has a hydrophobic sheath covering an inner wall of the outerbody; and an electrically nonconductive inner body having an axial fluidpassageway and an open end coaxially disposed within the outer body, anelectrode positioned outside the outer body for generating an electricfield at the open end of the inner hollow body.
 15. A nozzle for anelectric dispersion reactor according to claim 14, wherein the innerbody and the outer body are cylindrical.
 16. A nozzle for an electricdispersion reactor according to claim 15, wherein the electrode ispositioned adjacent the open end of the inner body.
 17. A nozzle for anelectric dispersion reactor according to claim 14, wherein the electrodeis positioned adjacent the open end of the inner body.
 18. A nozzle foran electric dispersion reactor according to claim 14, wherein thehydrophobic sheath is electrically nonconductive.
 19. A nozzle for anelectric dispersion reactor according to claim 14, wherein the inner andouter bodies are made from glass.
 20. An apparatus for producing metaloxide particles comprising:a nozzle having electrically nonconductiveinner and outer substantially coaxially disposed hollow bodies, theinner body delivering a disperse phase fluid into a continuous phasefluid within the outer body; and means for generating an electric fieldwithin the outer body at a level sufficient to disperse the dispersephase fluid into the continuous phase fluid.
 21. An apparatus accordingto claim 20, further comprising means for delivering continuous phasefluid through the outer body.
 22. An apparatus according to claim 21,wherein the continuous phase fluid has a flow rate in a range from about0 to 400 cc/min.
 23. An apparatus according to claim 20, furthercomprising means for delivering disperse phase fluid through the innerelectrode.
 24. An apparatus according to claim 23, wherein the dispersephase fluid has a flow rate in a range from about 0 to 40 cc/min.